Kenne Bell Twin-Screw Supercharger Kits

The performance world already knows to respect any machine sporting a Hemi, and a late-model, 6.4 Challenger is no exception. From a visual standpoint, the Challenger is certainly the best looking of the retro muscle cars, bettering both the Shelby Mustang and Camaro ZL1. In terms of all-motor performance, the 392-inch Dodge has the competition covered thanks to a power rating of 470 hp, but unlike Dodge, the competition has embraced factory installed power adders. Both the Shelby GT500 and ZL1 Camaro sport roots blowers on top of their already potent V-8s. Thanks to a little forced induction, the two supercharged power plants eclipse the 6.4 Hemi by over 100 horsepower.

What are the options, you ask, for a diehard Dodge owner? The best way to beat them is to join them, and add a little forced induction of your own. Chevy and Ford engines aren't the only ones that respond well to boost. One need look no further than the motivational force behind the fastest accelerating vehicles on the planet, supercharged Top Fuel motors, to see what Hemi horsepower is all about. Luckily for 6.4 Challenger owners, the 392 responds equally well to the benefits of boost. After extensive testing, Kenne Bell has satisfied the Challenger's need for speed by offering twin-screw supercharger kits for 2008-2012 Hemi (including 5.7, 6.1 and 6.4) powered vehicles. They are also hard at work on the new 2013/2014 applications. More than just the addition of boost, the Kenne Bell supercharger systems are the result of thousands of hours of research and development. Adding a supercharger to supply extra air to the engine is only half the battle, as the experts at Kenne Bell have taken supercharging Hemis to the next level by addressing the many issues associated with forced induction often overlooked by the competition.

To maximize power production and minimize unwanted heat generation, Kenne Bell chose the most efficient positive displacement supercharger design available. While most other manufacturers rely on the less expensive roots blower for their kit, Kenne Bell chose the more expensive (to produce) twin-screw design. Compared to roots blowers, the twin-screw supercharger offers both increased efficiency—thus lowering the inlet charge temperature, and a reduction in parasitic losses associated with turning the blower. It takes power to make power, but in the case of the twin-screw design, it takes less to make more. The result is increased air flow at a lower temperature, and a reduction in pumping losses that all add up to more (safe) power per pound of boost. Now toss in the dramatic difference in displacement compared to the typical roots blower kits for the Hemi, and you can see why the Kenne Bell kits have become so popular among Hemi owners. The smallest 2.8L supercharger (capable of 1,000 hp) offered by Kenne Bell is .5 liters larger (and more efficient) than the 2.3L roots blowers used by the competition. Now factor in the 3.6L (tested at 1,600 hp), and massive 4.2L, all which fit under the stock hood of the Challenger, and you start to see which supercharger is the obvious choice.

The twin-screw supercharger is certainly a huge step in the right direction, but Kenne Bell didn't just plop on an efficient twin screw and call it good. After all, what good is a trick supercharger if you neck down all that efficiency with a restrictive inlet system? Knowing from extensive testing that a supercharger is only as good as the inlet system feeding it, Kenne Bell upgraded the entire inlet system to accommodate the impressive flow rates offered by their massive superchargers. The result was the Mammoth intake manifold; a 41⁄2-inch inlet system and (optional) 148-mm throttle body. While others rely on optional air intake systems to replace the very restrictive factory air box, a simple open-element filter in the engine compartment is not a viable (or smart) option. Hot air is the enemy of performance, and a direct route to detonation. Kenne Bell has exceeded 650 horsepower using the Mammoth intake, 41⁄2-inch inlet system and stock throttle body, but if you are looking to gain an extra 25 (or more) horsepower, or wanting to take your Hemi above 700 wheel horsepower, opt for the 148-mm throttle body that effectively doubles the flow rate of the stock unit. The Mammoth intake and 41⁄2-inch inlet system are already sized to handle the extra flow offered by the throttle body upgrade.

The efficiency of the twin screw, along with the reduced parasitic losses associated with driving the blower, allow the use of a six-rib serpentine drive belt, with the blower sharing duty with the remainder of the accessories. In fact, the nine-second, supercharged 426 stroker tested here relied on nothing more elaborate than a six-rib belt! Fuel system upgrades for the standard supercharger kit were equally simplistic, consisting of nothing more than 50-pound injectors and a 17V Kenne Bell Boost-a-Pump to supply the necessary fuel flow. According to Kenne Bell, the Boost-a-Pump combined with the injector upgrade will support up to 650 wheel horsepower, with larger injectors and a 20V Boost-a-Pump taking that number to 775 wheel horsepower. Since even the 2.8L supercharger will support much more than that, additional power will require further fuel system upgrades. The 426 stroker utilized a fuel system from ST Motorsports consisting of a Fore hat and regulator, a pair of 405 Walbro fuel pumps and 80-pound injectors. The additional power potential of the combination was one consideration but so too was the extra flow required by the use of E85 fuel (25-30 percent more than gas).

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1. The 2010 Challenger received a 2.8L, twin-screw supercharger capable of supporting over 1,000 hp. Recognizing that less air into the blower means less boost and power out, Kenne Bell went to the trouble of designing a dedicated Mammoth intake manifold to feed the supercharger.

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2. To maximize flow to the Mammoth intake manifold, the Kenne Bell twin-screw kit included a massive 41⁄2-inch (true) cold-air intake system. The Mammoth intake was designed to accept a variety of different throttle bodies ranging from the stock 81-mm unit that flowed 924 cfm to a Kenne Bell 148-mm throttle body that flowed a whopping 1,880 cfm.

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3. Obviously, a supercharged engine requires more fuel. For our application, this kit included a billet fuel rail equipped with 50-pound injectors.

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4. The 6.4L kit comes with a blower pulley designed to provide 61⁄2 psi of boost for use with 91 octane, and 71⁄2 psi with 93 octane. Add race fuel or E85, and an extra 200 horsepower is a simple pulley change away.

This installation and test regiment was typical of what a Challenger owner can expect from a Kenne Bell supercharger. Since the Kenne Bell kit was designed to fit the automatic Challenger as well, they went to the extra effort of testing a stick versus an automatic at a variety of different boost levels. In stock trim, the manual transmission car produced 434 wheel horsepower while the automatic car produced 419 horsepower. The stick offered more power as expected, but the gains came primarily at the top of the rev range. The slight power advantage offered by the stick continued at each boost level, as Kenne Bell ran the boost up on the stock vehicles during testing to a maximum of 11 psi where the stick car exceeded 700 wheel horsepower (with the optional 148-mm throttle body). According to Kenne Bell, the use of higher compression and a weaker piston (thinner ring lands) in the 2011-13 6.4 required a lowering of boost from the previous 6.1 kits. The standard kit for the 2011-13 Hemi from Kenne Bell will provide 61⁄2 psi of boost for use with 91 octane, or 71⁄2 psi with 93 octane. Higher boost levels are possible with race fuel or E85, which can allow as much as 10 additional psi of boost. Run with a 2.8L blower at the 6.5 psi required by 91 octane, the 2010 Challenger produced 569 horsepower and 507 lb-ft of torque. These numbers jumped to 586 horsepower and 543 lb-ft of torque at 71⁄2 psi.

Graph: 2010 6.4L Manual Challenger-NA vs KB SC (6.5-11 psi)

The graph illustrates what happened when we tested the 6.4 Hemi with the Kenne Bell supercharger kit. In stock trim, the Hemi produced 434 horsepower and 429 lb-ft of torque. After installation of the Kenne Bell twin screw, the power numbers jumped to 569 horsepower and 507 lb-ft of torque at 61⁄2 psi. Stepping up in boost resulted in 586 horsepower at 71⁄2 psi, 641 horsepower at 9 psi, and 683 horsepower at 11 psi. This further increased to 709 horsepower with the installation of the larger 148-mm throttle body.

Test 2-2011 Auto 6.4L Challenger (426 Stroker)

With the ability to exceed 700 wheel horsepower on a stock engine, we obviously couldn't help but wonder what might happen if we combined that boost with a stroker engine. Built by BES Racing Engines for owner Bill Sharing, the 9.5:1 426 stroker featured a Callies crankshaft, Manley rods, and forged pistons. Ported heads worked in conjunction with a Comp cam, Kooks long-tube headers, and a complete 3.6L Kenne Bell supercharger kit. What is most amazing about this combination is not the power, but how well it drives. Machines that rip off nine-second passes at 136 mph are not supposed to idle in traffic and perform the mundane task of the daily commute. Thanks to the combination of a Paramount Transmission and a Jeep 3,000-rpm stall converter, the Challenger was not only able to post power numbers of 882 wheel horsepower at 18 psi on E85, but do so with surprising civility. The 882 wheel horsepower translates into more than 1,000 flywheel horsepower, a serious amount for any street car. Thanks to immediate boost response, twin-screw superchargers excel at torque production, and this Kenne Bell Hemi application was no exception. The supercharged stroker thumped out over 800 lb-ft of torque, and never dropped below 700 lb-ft from 3,500 rpm to 6,400 rpm.

Graph: 2011 Auto 426 Stroker Challenger- NA vs KB SC (18 psi)

We included a baseline test from a stock automatic 6.4 Hemi, but this Challenger was sporting no less than 426-inches of BES stroker engine. The modified stroker was combined with boost from a 3.6L Kenne Bell to produce peak numbers of 882 horsepower, and 803 lb-ft of torque at 18 psi. This car has dipped into the nines with what can best be described as stock suspension—amazing.

Price Tag

Part

PN

Cost

Mammoth 2.8L ('08-'10 5.7 Hemi)

TS7500-5.7

$6,999

Mammoth 3.6LC ('05-'12 5.7, 6.1 Hemi)

TS7501-3.6LCTUN

$7,649

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6. Kenne Bell blowers feature a revolutionary liquid cooling option, used to stabilize the temperature differential between the inlet and discharge sides of the rotor pack. Keeping things cool on every Kenne Bell Hemi kit was an efficient air-to-water intercooler.

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7. Anytime modifications like adding boost are done, the fuel system must be improved. Fuel system upgrades with the stroker 426 included a billet fuel hat (not shown) and adjustable fuel pressure regulator. If you're planning to use E85 with elevated power levels, this will require filling the billet fuel rails with 80-pound injectors.

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8. Available in 17V and 20V configurations, the Kenne Bell Boost-a-Pump is the hot set up for dramatically improving the flow rate of any fuel pump. The BAP can be used with larger injectors to support 775 wheel horsepower, all without dropping the fuel tank. Beyond that, a pump change will be necessary. The 1,000-plus horsepower stroker required the installation of a 20V BAP, and dual Walbro in-tank pumps.

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9. Run on the dyno, this Challenger ripped off 882 rear wheel horsepower and 803 lb-ft of rear wheel torque. Despite the massive power and nine-second time slips at 136 mph, this supercharged Challenger can be driven by your Grandma.

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10. The graph illustrates what happened when we tested the 6.4 Hemi with the Kenne Bell supercharger kit. In stock trim, the Hemi produced 434 horsepower, and 429 lb-ft of torque. After installation of the Kenne Bell twin screw, the power numbers jumped to 569 horsepower and 507 lb-ft of torque using 61⁄2 psi. Stepping up boost resulted in 586 horsepower at 71⁄2 psi, 641 at 9 psi, and 683 at 11 psi. This increased further to 709 horsepower with the installation of the larger 148-mm throttle body.